patrick.meyers@LIGO.ORG - posted 16:31, Monday 02 November 2015 - last comment - 09:19, Tuesday 03 November 2015(23053)
H1 Whistles
[detchar whsitle team]
We see DARM whistles in H1 on October 30th. They are also seen in the REFL_SERVO channel. The plots below illustrate glitch frequency vs. PSL VCO frequency at the time of the glitch (color is log10(omicron snr)). They do not appear to couple below 2 kHz, and the whistle frequency that appears in DARM is very, very loud in REFL_SERVO.
Further investigation is ongoing for other channels and over recent locks for the last several days to try to pinpoint when this started.
Images attached to this report
Comments related to this report
The frequency of the crossing that we see in DARM is 79.073 MHz, and these RF whistles track the beatnote, not the harmonic (i.e. the absolute value of the PSL VCO frequency minus this fixed value). The other two lines seen in REFL servo are 79.1385 MHz, also a direct coupling, and 79.0018 MHz which seems to follow twice the frequency difference. We don't see these lines coupling in FSS mixer, ISS AOM driver, or MICH. Not seeing it in MICH (while we do in SRCL and PRCL) is maybe evidence that this is coupling through frequency noise. We should look over more locks at how these appear in the above-mentioned channels, and compare to L1 where things are much more complicated.
Images attached to this comment
